The 'tts:origin' attribute for element 'region' on line 11 uses pixel positioning, but there is no extent on the tt element. Positioning will be ignored.

The root element must be 'tt'. Was 'null'

Definition:

The TTML file has a schema issue that may cause presentation issues. While the file may conform to the TTML spec, it is not compliant with current accepted practices, and the subtitle may not display as intended. The error message will include details of what is exactly wrong.

Solution:

Ensure that values set in your TTML files are valid and supported. Please review the error, correct the issues in the TTML file and redeliver.